Method and apparatus for the production of artificial fibers



May 16, 1939. A.FORMHALS 2,153,416

METHOD AND APPARATUS FOR THE PRODUCTION OF ARTIFICIAL FIBERS Filed July28, 1957 5 sheets-sheet 1 FIG. 2..

INV EN TOR.

A TTORNEYS.

May 16, 1939. A. FORMHALS 2,158,416

METHOD AND APPARATUS FOR THE PRODUCTION OF ARTIFICIAL FIBERS Filed July28, 1937 3 Sheets-Sheet 2 IN V ENTOR.

ATTORNEYS.

ay 16, 1939. FQRMHALS 2,158,416

METHOD AND APPARATUS FOR THE PRODUCTION OF ARTIFiCIAL FIBERS Filed July28, 1937 s Sheets-Sheet .3

FIG. 6.

IN VEN TOR.

A TTORNEYS.

Patented May 16, 1939 PATENT oFFicE METHOD AND APPARATUS FOR. THE PRO-DUCTION OF ARTIFICIAL FIBERS Anton Formhals, Mainz, Germany, assignorof. forty-five one-hundredths to Richard Schreiber-Gastell, Mainz,Germany Application July 28, 1937, Serial No. 156,169

11 Claims.

This invention relates to the production of artificial fibers, and moreparticularly, relates to a new process and apparatus for electricallyspinning artificial fibers. By electrical spin ning is meant thedispersion or shattering of a stream of spinning solution by means of ahigh electrical potential.

It has been disclosed in Formhals U. S. Patent No. 1,975,504 thatsolutions of filament-forming materials may be spun into fibers bycausing the spinning solution, in the form of a stream, to be extrudedbetween two electrodes bearing electri-' cal charges of high potentialand opposite polarity; one of the electrodes being the spinning jet, andthe other electrode comprising a moving collector for the fibers. Thehigh potential electric charge on the spinning jet is apparentlytransmitted to the spinning solution and causes the same to be shatteredor dispersed to produce a multiplicity of charged fibers or filamentswhich are attracted to and collected on the moving electrode.

Some difiiculty is experienced in this method of electrical spinningfrom the annoying tendency of certain stray fibers to becomeelectrostatically charged with a charge of the same polarity as thecollecting electrode as it approaches the same, whereby the fibers tendto travel back into the electricalfield surrounding the solution feedingdevice. For example, a fiber leaving the spinning jet may be chargednegatively, but as it approaches the. field of the collecting electrode,the fiber may become positively charged from the collecting electrodebefore it reaches the latter. In this case the positively chargedcollecting electrode will repel the positively charged fiber which, as aresult, never reaches the collector. In some cases the fibers maytemporarily adhere to the collecting electrode, but due to the highelectrical potential thereon, are repelled and thrown back to the jetelectrode. Otherfibers, after reaching the collecting electrode andpartially adhering thereto, are positively charged and the ends thereofwhich have not had an adequate opportunity to attach themselves to thecollecting electrode are projected outwardly at an angle to thecollecting electrode and generally give a sliver having poorcharacteristics. The stray fibers which happen to fiy back into theproximity of the jet electrode tend to become attracted and attached tovarious parts of the jet electrode. The fibers may thus accumulatearound the spinning jet electrode to a sufiicient extent to causeserious interference to thefree and continuous delivery of the spinningsolution.

In copending application to Anton Formhals, Serial No. 88,431, filedJuly 1, 1936, the difilculty due to stray fibers is overcome to a largeextent 5 by maintaining the electrical potential of the collectingelectrode substantially lower than the electrical potential on thespinning jet electrode.-

This lower potential on the collecting electrode is secured, forexample, by means of an air gap 1 placed between the source of theelectrical potential and the collecting electrode. Such a procedure isa'decided improvement over that of Formhals U. S. Patent No. 1,975,504,but has still the disadvantage that the collecting device is 15 chargedand therefore dangerous from the standpoint of fire hazard and thesafety of the operator. In addition, the air gap has to be frequentlyadjusted since the charge on the collecting electrode varies withsuch'factors as the 20 type of solution being spun, the temperature andhumidity of the air, the distance between the collecting electrode andthe spinning jet electrode, and the total, electrical potential betweenthe two electrodes. Moreover, if the air gap is 25 too large between thesource of the electrical potential and the collecting'electrode, one isfaced with the disadvantage of the fibers overshooting the collectingelectrode with resultant waste from the fibers flying about the spinningroom.

It is therefore one object of the present invention to provide anelectrical spinning process wherein good collection of the fibers issecured primarily by the position of the collecting device with respectto the spinning jet electrodes rather than by the amount ofelectrostatic potential on the collecting device.

Another object ofthe present invention is to devise a novel process forthe electrical spinning I of fibers. 40

Still another object of the invention is to overcome the difiiculty dueto stray fibers in the electrical spinning of fibers.

Specifically, the object of the invention is to electrically spin fibersfrom oppositely charged sets of jet electrodes, the said sets beingplaced on opposite sides of a moving collecting device.

Accordingly the invention embraces a process comprising electricallyspinning a spinning solution from sets of jet electrodes, each sethaving preferably a substantially equal but opposite electrical chargefrom that on the other, collecting the oppositely charged fibers on amoving collecting device that is placed in the electrically 55 neutralarea between the oppositely charged, relatively symmetrical electricalfields.

By the term electrically neutral area we refer to the area of zeropotential between oppositely charged electrical fields.

By the term non-electrode as applied to the collecting device, is meanta collecting device which is not charged with a high electrical potential and which, therefore, may be touched by an operator without danger.

In the preferred embodiment of the invention, the spinning solution isextruded from two sets of spinning jet electrodes, each set bearing ahigh electrical potential of equal and opposite charge, and the chargedfibers are collected in j the form of a sliver on the tips of aplurality of metallic prongs fastened to a belt which may be constructedof rubber, leather, canvas, cambric or other suitable material. The beltwith its prongs is preferably grounded and so positioned with respect tothe two sets of spinning jet electrodes that it moves through theelectrically neutral area between the two oppositely charged electricalfields. Each of the two sets of spinning jet electrodes is regulated todeliver substantially the same amount of spinning solution.

In order to more clearly set forth the premnt invention, reference ismade to the following detailed description taken in connection with theaccompanying illustration, in. which:

Figure 1 is an end elevational view, partially in section, showing theoppositely charged spinning jets and the collecting device of anapparatus constructed in accordance with this invention.

Figure 2 is a top plan view of the apparatus shown in Figure 1;

Figure 3 is a top plan View of an electrical spinning apparatusincluding a means for grounding. the collecting device;

Figure 4. is an end elevational view, partially in section, showing amodified form of electrical spinning device;

Figure 5 is a diagrammatic illustration of a modified form of theinvention;

Figure 6 is a side elevational view of the apparatus shown in Figure 5.

Referring to the drawings, a spinning solution from storage tanks l2 andH2 is supplied to a plurality of metal spinning jets to and i0, whichare connected respectively to the pipes it and it. The spinning jets l0and i0 and pipes M and l I are charged with a high electrical potentialof equal and opposite charge by being electrically connected to oppositepoles oi a device l3 for producing high potential electric current.Device it may be a transformer and rotary convertor for changingordinary line current, such as 110 volt-60 cycle, alternating electriccurrent, into a high voltage, pulsating, electric current, or I3 may beany suitable device for producing a high potential direct current. Forobtaining special effects in the shattering of a. stream of spinningsolution, it may be a suitable device for producing an alternatingcurrent of high potential of any desired or varying frequency.

Spaced equidistant from the two sets of spinning jet electrodes i0 andi0 is a. long, endless belt ht preferably comprising rubber or any othersuitable, non-conductive material, although an electrically conductingmaterial such as metal may be used. The belt is provided with spacedmetal prongs or lugs 85 which are fastened to the belt so as to projectfrom both sides thereof. The prongs l5, which arepreferably pointed attheir ends projecting from the sides of the belt,

are disposed substantially within the plane of the belt, with theprojecting ends extending perpendicularly from the side of said belt.The belt is driven by pulleys l6 and H which are preferably composed ofwood or some other suitable, electrically non-conducting material. Theoppositely charged sets of jet electrodes in and it are positioned adistance apart at least equal to and preferably more than the distancebetween the jet electrodes and the collecting device, and far enoughapart to prevent sparks jumping across between the sets of jetelectrodes and creating a fire hazard. The collectingbelt is positionedat such a distance from the electrodes that the spinning solution willbe well dispersed or shattered into separate filaments before theycontact with the prongs B5. The belt is furthermore positioned somewhatlower than the spinning jets and with the points of the prongsprojecting from one side of the belt spaced at substantially an equaldistance from jets l0 as the oppositely projecting ends of the prongsare spaced from jets l0. In this manner, the fibers produced from thesolution flowing from jets ill will collect on the ends of the prongsprojecting from one side of the belt and the fibers from the solutionsissuing from the opposing set of jets are collected on the opposite endsof the prongs in the form of continuous slivers 20 and 20. Theelectrical charges on the fibers collecting on one side of the belt areopposite to those collecting on the other side and will neutralize eachother to maintain the belt collector substantially neutral.

In the preferred embodiment of the invention, an electrically conductiveelement i8 is positioned on the collector belt to electrically connectthe individual prongs 65 to each other. An electrically groundingmechanism is can be contacted with the element it so as to prevent thepresence of an electrical charge on the prongs or belt in case the beltis inadvertently forced closor to one set of spinning jets than to theother wt. The grounding mechanism may comprise a trolley with thetrolley wheel having continuous rolling contact with the element l8. Itis to be understood, however, that the apparatus will be operativewithout the element l8 and the grounding mechanism.

The electrical potential on the jet electrodes between the sets of jetelectrodes may be-varied between 10,000 and. 100,000 volts andpreferably is maintained at a potential of at least 30,000 volts. Sincethe resistance from the device it to the sets of jet electrodes is equaland since there is no leakage of the voltage, the potential charge oneach set of electrodes is substantially equal I and opposite in charge.

Potential stabilizing and directing means 30 and 30", comprising, forexample concavely curved metallic screens or strips are preferablypositioned in back of the jet electrodes l0 and W. The means 30 and 30'are connected to a charge of highelectrical potential of the samepolarity as the potential on the corresponding sets of jet electrodes.The directing means serve to direct the charged fibers towards theprongs of the belt and to overcome any difference in symmetry of theelectrical field surrounding the jet electrodes.

The-potential stabilizing and directing means is the subject of mycopending application Serial No. 88,430, filed July 1, 1936, andreference is made to the said application for details thereof.

The following detailed example of one embodiment of a process forcarrying out the present I 2,158,418 I v the spinning solution isextruded from oppositely invention is given as a specific illustrationand is not to be considered as limiting the scope of the invention.

Example A solution having a viscosity at 25 C. of 35.7 poises andconsisting of 150 grams of cellulose acetate, 600 grams of acetone and300 grams of the monomethyl ether of ethylene glycol is forcedthroughtwo opposing sets of single hole jet electrodes, the orificediameters of which are approximately 0.0180 inch. Opposite poles of asource of pulsating, direct current of 50,000 volts are connected toopposing sets of jet electrodes. The streams of cellulose acetatesolution are broken under the influence of the high electrical potentialexisting between the charged jets and a moving collecting belt intonumerous fine filaments which are deposited on and carried away by theprongs of the moving belt. The charged fibers from one set of jetelectrodes, upon deposition, apparently impart a charge to the oppositetip of the metal prong upon which are attracted, collected andneutralized the oppositely charged fibers from the other set of jetelectrodes. The net result is that the belt remains substantiallyelectrically neutral and two essentially uncharged slivers are collectedon the tips of the prongs. To insure that the streams of solution andthe fibers produced therefrom are properly directed to the prongs, thebelt is placed in the electrically neutral area between the electricalfields surrounding the oppositely charged sets of jet electrodes andbelow the electrode jets at a distance which essentially represents abalance between gravity and electrical forces exerted on the solutionand the fibers. The fibers may additionally be directed upon the prongsby means of metallic screens positioned back of the jet electrodes andpossessing an electrical charge of the same sign as that of theelectrode. During the dispersion or shattering of the stream of solutionand, deposition of the fibers, the solvent evaporates, the fibersquickly drying as they are carried away from the spinning zone. Thefibers are thus oriented in a position substantially parallel to thedirection of travel of the belt and due to their rapid drying andsubstantial freedom from electrostatic charge, adhere neither to theprongs nor to one another, to any objectionable degree. The continuoussliver thus formed is removed by a stripping device and deposited in asuitable container or wound on a reel. Prior to drawing or twisting, andpreferably prior to winding the sliver, it is treated with a suitabletextile finish in a fashion similar to the treatment of wool rovings soas to facilitate the ease and smoothness of drawing. The silver treatedwith a suit able textile finish is drawn and/or twisted to yield a yarnof any weight desired.

In another form of the present invention the oppositely charged sets ofjet electrodes are positioned relatively close together and at aconsiderable distance from any ground, such as the belt mentionedhereinbefore. As a result, the oppositely charged fibers sufiicientlyattract one' another and as they come in contact they neutralize thecharge on each other. The neutralized fibers fall by gravity andpreferably are collected continuously in the form of a sliver-likebundle on a collector, for example, an endless belt. This mode ofoperating the invention also offers an excellent procedure for producingstaple in a fiuffed form.

Referring to Figure: 5 and 6 of the invention,

charged sets. of spinning jet electrodes l0 and I0, each set consisting,for example, of 20, 50, 100 or more jet electrodes. The spinningsolutions are electrically dispersed into fibers which are attracted toeach other along a line intermediate the sets of spinning jets. As thefibers eontact each other, they become neutralized and fall to the belt40 and are carried away to a container or wind-up device. If desired,the fluffed staple fibers may be permitted tofall by gravity to thefioor and then removed by suction, by a stream of air or fluid, or by abelt or other mechanical means. The fiuifed staple may be converted intoa sliver by the usual textile operations.

Referring to the modification of the invention illustrated in Figure 4of the drawings, reference numeral 50 designates a source of highpotential alternating current such as a transformer in which lowpotential alternating current such as 110-120 volt 60 cycle current istransformed to 10,000 to 100,000 volt 60 cyclecurrent. Lead wires 52 and54 connect to a source of low voltage alternating line current and tothe low voltage side of the transformer 55. Lead wires 56 and 58 areconnected between the high voltage terminals poles of rotary converter65. Lead wires 64 and 66 are connected between the direct current poles.

of rotary converter and to the pipe lines I I and II respectively. Alead wire 60 is connected to lead wire 58 (or 56) and to trolley 10. Thewheel 12 of the trolley contacts the element I8 which connects thevarious prongs l5 or belt Id. In this modification, it may be desired toplace an air gap or other resistance designated by El in lead 60. Thefunction and utility of such an air gap or resistance is specificallydisclosed in my copending application Serial No. 88,431, filed July 1,i936.

In operation the prongs will be alternately charged with a positive andnegative high potential in accordance with the frequency of thealternating current. The prongs l5 will therefore have an alternateattraction and repulsion for the fibers. alternation is a small fractionof a second, it will not prevent the adherence of the fibers to theprongs for the formation of a sliver thereon. The alternations, however,have the desirable function of giving a curliness or crimp to the fiberssince they are alternately attracted and repelled' Inasmuch as thefrequency of thefore, does not have some of the desirable features ofthe other modifications in which the belt and prongs carry no dangeroushigh potential charge of electricity, but has certain other advantagesnot possessed by the previously described modifications. The variousmodifications are all com-' mon to each other, however, in that theyhave opposing sets of jet electrodes connected to opposite poles of asource of a high electrical potential.

While the rate of delivery of the spinning solution from the sets of jetelectrodes may be varied with respect to one another within a limitedrange, still it is preferred for most satisfactory operation that therate of delivery be substantially the same from each set of jetelectrodes. Likewise, while preferred, it is not ab- .solutely necessaryto have the potential equal on the oppositely charged sets of electrodejets, some solvents in the spinning solution will cause a greater orlesser shattering of the liquid stream than others and some solutionswill require a higher potential than others for the satisfactory tillbreaking up of the stream and the formation of fibers. Solutions ofother cellulose esters, for instance cellulose propionate, celluloseaceto-propionate, cellulose aceto-butyrate, cellulose acetostearate andsolutions of cellulose ethers such as ethyl or benzyl cellulose may alsobe spun by the procedure of the invention. Generally, solutions ofresins, molten glass or other materials which may be formed into fibersmay also be spun in accordance with the method of the invention. It hasbeen found that polymerized resins of alkyl esters of acrylic acids, andspecifically polymerized methyl methacrylate resin, can be electrical-1y spun to produce particularly desirable fibers.

These acrylic acid resins may be dissolved in suitable solvents, such asacetone together with a suitable plasticizer if desired and electricallydispersed or shattered in the same manner as the spinning solutionsabove described.

The moving collecting device which may or may not be grounded, on whichthe fibers are collected in a continuous sliver, may be driven at anydesired speed to obtain varying effects. However, when it is desired tocollect the fibers in a compact, coherent sliver, in which the fibersare arranged substantially parallel to each other, it is essential thatthe linear speed of the collecting device be at least as high as, andpreferably higher than the speed of the freshly formed fibers in theirtravel towards the collecting device. It is preferred that thecollecting device be a continuance belt with prongs. However, it maycomprise any other form of collecting device such as a wheel, in whichcase one sliver is continuously formed. Or, the collector may be someother device provided, like the belt, with prongs around itscircumference, which prongs are adapted to mesh with a suitable meansfor removing the sliver from the collection device. If desired, suitablypositioned air jets may be used to remove the sliver or may be used inconjunction with various mechanical devices in removing the sliver fromthe collecting mechanism.

Suitable delustering agents such as pigments, oils, organic solids andsimilar materials may be introduced into the spinning solution toproduce delustered, semi-lustrous and other effects. Likewise. dyedfilaments or fibers may be spun by. introducing suitable dyes or othercoloring matter into the solution.

The process of the invention as illustrated in Figures 1, 2, 3 and 5oflers greater ease in controlling the uniformity of the electricalspinning operation in that it utilizes a collecting device that is notan electrode in the sense that the collecting device is not connected toan electrical potential, either directly or through an air gap.

arcane As a result, the operating conditions may be varied over a widerrange than in previous methods since inherently the procedure is notaffected so critically by factors such as humidity and temperature, thedistance between the jet electrodes and the collecting device, and thefluctuations in electrical potential, and changes in the electricalpotential. Since there is no high electrical potential wire relativelyclose to the collecting device, the danger of operators suffering fromelectrical shock or from explosions due to electrical sparking 1n thepresence of solvent vapors is practically eliminated.

The process of the invention as illustrated in Figure 4 has theadvantage of forming a sliver composed of very curly or highly crimpedfibers which more nearly simulatewool.

Economically, the process of the invention in accordance with all of themodifications afiords a relatively cheap and emcient mode ofelectrically spinning and collecting fibers and also utilizes fioorspace emciently.

It will be obvious that many changes and modificatlons can be made inthe above described apparatus and processes without departing from thenature and spirit of the invention. It is therefore to be understood theinvention is not to be limited except as set forth in the appendedclaims,

I claim:

1. In an apparatus for the electrical spinning of fibers a set ofspinning jet electrodes, a second set of spinning jet electrodes spaced,from said first set, means for connecting said sets of jet electrodesto opposite poles of a source of high electrical potential, a movingcollecting means positioned substantially in the neutral zoneintermediate said sets of jet electrodes for collecting fibers from bothof said sets of jet electrodes, the space between said sets of jetelectrodes being sufliclently great to prevent the passing of a sparktherebetween due to their opposite charges of electricity and beingsufficiently small to cause an attraction to each other of theoppositely charged fibers spun from the said jet electrodes.

2. In an apparatus for the electrical spinning of fibers a set ofspinning jet electrodes, a second set of spinning jet electrodes spacedfrom said first set, means for connecting said sets of jet electrodes toopposite poles of a source of high electrical potential, a movingcollecting means positioned below and substantially in the neutral zoneintermediate said sets of jet electrodes, the space between said sets ofjet electrodes being sufficiently great to prevent the passing of aspark therebetween due to their opposite charges of electricity andbeing suificiently small to cause an attraction to the collecting meansof the oppositely charged fibers spun from, the said jet electrodes.

3. In an apparatus for the electrical spinningof fibers a set ofspinning jet electrodes, a second set of spinning jet electrodes spacedfrom said first set, means for connecting said sets of jet electrodes toopposite poles of a source of high electrical potential, a, movingcollecting means having prongs projecting from opposite sides thereofpositioned below and substantially in the neutral zone intermediate saidsets of jet electrodes, the space between said sets of jet electrodesbeing suficiently great to prevent the passing of a spark therebetweendue to their opposite charges of electricity and being sufficientlysmall to cause an attraction of the fibers spun from one set ofelectrodes to the prongs projecting from one side of the collectingmeans and an attraction of the fibers spun from the other set ofelectrodes to the prongs projecting from the other side of thecollecting means.

4. In an apparatus for the electrical spinning of fibers as defined inclaim 1, means connected to said collecting device to maintain the sameelectrically grounded.

, 5. In an apparatus for the electrical spinning of fibers as defined inclaim 3, means connected to said prongs to maintain the sameelectrically grounded.

6. In an apparatus for the electrical spinning of fibers as defined inclaim 3, meansconnected to said prongs to alternately impart thereto ahigh potential of opposite sign.

7. In a process for the electrical spinning of fibers, the step whichcomprises imparting a high electrical potential of opposite sign tospaced streams of spinning solution whereby to cause them to beelectrically shattered into fibers, and collecting said fibers on acollecting means common to said spaced streams.

8. In a process for the electrical. spinning of fibers, the-stepscomprising extruding a plurality of streams of spinning solution fromone zone, extruding a second plurality or streams of spinning solutionfrom a second zone, imparting high electrical potentials of oppositesign to the streams of spinning solution in said two zones respectively,said zones being separated a distance suflicient to prevent electricalsparks being created therebetween but which will permit the resultingspun fibers to be attracted to each other, and collecting said fibers ona collecting means common to said plurality of streams.

9. In a process for the electrical spinning oi fibers, the stepscomprising extruding a plurality of streams of spinning solution fromone zone,

extruding a second plurality of streams of spinning solution froin asecond zone, imparting high electrical potentials of opposite sign tothe streams of spifining solution in said two zones respectively, saidzones being separated a distance sufiicientto prevent electrical sparksbeing created therebetween, and collecting the fibers from said twozones on opposite sides of a. collecting device positioned therebetweento form two independent slivers of-fibers.-

10. In a process for the electrical spinning of fibers, thestepscomprisingextruding a plurality of streams of spinning solutionfrom one zone, extruding a second plurality of streams of spinningsolution from 'a second zone, imparting high electrical potentials ofopposite sign to the streams of spinning 'solution in said two zonesrespectively, said zones being separated a distance sufiicint to preventelectrical sparks being created therebetween, and collecting the fibersfrom said two zones on opposite'sides of a'collecting device positionedin an electrically neutral zone therebetween to form two independentslivers of fibers.

11. In a process for the electrical spinning of fibers, the stepscomprising extrudinga plurality oi streams of spinning solution from onezone,

extruding a second plurality of streams oi spinning solution from asecond zone, imparting high electrical potentials of opposite sign tothe streams of spinning solution in said two zones respectively, saidzones being separated a distance suilicient to prevent electrical sparksbeing.

created therebetween but which will rmit the -resuiting spun fibers tobe attracted to each other, j and collecting said fibers in the form ora single sliver substantially in a neutral zone intermediate saidextruding zones.

an'ron roams.

